There are currently three types of bed scales available for use in weighing a person lying in a bed. The bed scales are either "built-in, .... under-bed," or "bedside."
"Built-in" scales are designed into the bed frame by the bed manufacturer and are usually encountered in higher priced, critical-care bed systems. They can be substantially more expensive than other types of scales, including scales according to the present invention.
"Built-In" scales inherently are unable to be transported from bed to bed. They require the purchase of an entire bed frame specially designed with the "built-in" scale installed. They are not retrofittable to existing bed frames. A patient must be in one of the specially designed "built-in" scale bed frames in order to be weighed. If not, the patient must be moved to that specific bed frame. As the study that is discussed below indicates, when a patient's weight is most desired, movement of the patient is least likely to be in the patient's best interest. Moving the patient is least desirable when the patient is critically ill, and yet this is when the patient is most likely in need of having his/her weight monitored. The relatively high expense of these scales can result in the hospital or care center being unable to afford many of such beds.
Another difficulty with "built-in" scales is that anything hanging on the bed frame can cause error in most of the weighing systems. The error is caused when the scale is initially zeroed out and then items such as urine bags (Folley bags), drug pumps, CPR equipment and the like are hung on the bed frame. The equipment weight causes the scale to include this in the patient's weight, resulting in an incorrect reading of weight. A scale according to the present invention can be independent of both the mattress and the frame of the bed. Therefore, anything hanging on the frame of the bed will not affect the scale or its reading of the patient's weight.
The "under-bed" scales are designed as a ramp for the bed to be rolled onto. The "under-bed" scales can provide continuous monitoring of the total combined weights of the bed, bedding, and patient. These scales typically come as two part systems. One section is used at the head of the bed while the second section is used at the foot of the bed. The installation of these scale systems requires proper ramp placement and alignment so that each of the four bed wheels can be rolled onto the weighing platforms in unison and thereafter be properly positioned on the weighing mechanisms.
These "under-bed" scales are not conveniently transportable, and they are expensive. These "under-bed" scales are relatively difficult to maintain, and often require specially trained personnel to operate them. If these scales are ever moved for use with another bed, they usually require re-calibration by specially trained personnel. Therefore, "under-bed" scales are often both difficult and expensive to install and to maintain.
Finally, there are two types of "bedside" scales. The first type is known alternately as a sling, hammock, or stretcher scale. This scale consists of a canvas type material that is slipped under the patient in the manner of a stretcher. The canvas is then attached to an overhead hoist which lifts the patient from the bed for weighing. The second type of "bedside" scale, sometimes referred to as a litter scale, operates similarly. However, instead of having a canvas sling, this type of scale has a rigid board which lies parallel to the bed, requiring patient transfer before and after weighing.
The need for accurate monitoring of fluctuations in patient body weight has become increasingly important to the medical community in recent years. This fact is being continually reinforced through comments by clinicians, nurses, and in scientific journals. Doctors must constantly tailor medications and specialty treatments according to a patient's weight or weight change. This type of customized health care is essential to providing safe and effective wound or disease management and prevention. One study in the New England Journal of Medicine describes a desire by medical personnel to observe a patient's weight within plus or minus one pound. For the complete text, see Kay Schlegel-Pratt & William D. Heizer, How Accurate are Hospital Scales?, 320 NEW ENG. J. MED. 189 (Jan. 19, 1989).
Another study, in the Journal of Parenteral and Enteral Nutrition, states that "[d]eterminations of body weight are important in most hospitalized patients and especially in those individuals receiving nutritional support to monitor fluid balance and to measure nutritional therapeutic efficacy. Actual tissue gains and losses of greater than 0.5 pounds/day are almost impossible. Weight changes greater than this reflect changes in total body water, a clinically relevant fact with therapeutic implications." For the complete text, see Peggi A. Guenter, et al., Body Weight Measurement of Patients Receiving Nutritional Support, J. PARENTERAL AND ENTERAL NUTRITION 441-43 (1982). Part of the Guenter study included eliciting "what factors the nurses felt needed to be changed in order to improve obtainment of weights." One of the three most important items that the nurses felt could be changed to increase weight measurement was "scales broken or unreliable." In addition, a number of nurses expressed a concern which was "focused on equipment problems such as litter scales being unavailable, broken, too cumbersome or uncomfortable for the patient."
Other reasons for not obtaining patient weights included "patient refuses" and "nursing staffing shortages." The article postulated that "Patient cooperation may increase if they are not awakened . . . [and required to be moved] to be weighed." The patients were required to either get out of bed and use a standup scale or had to be moved in order to use a litter scale. In use of the present invention, there is no need to move the patient or to require the patient to get out of bed to use a standup scale. Also, it does not require extensive use of nursing staff. The medical personnel need only briefly look at the scale readout unit and note the weight on the patient's chart. Medical personnel do not have to move or wake up the patient.
The Guenter article also stated that "[m]easurements of height and weight are considered by some to be indicators of nutritional status. Serial weight measurements are clinically useful in determining a patient's fluid status and therefore in monitoring the nutritional regimen." The study then examined the likelihood that a patient would have their weight monitored regularly. The weights were least often-obtained for patients that were the most critically ill. However, even though the importance of weight measurement was expressed to the medical personnel, the "[l]ack of weights clustered in the intensive care units with patients in whom weight obtainment may be most clinically useful." The weights of intensive care patients were often not obtained, even though weight measurement was required for these patients.
The two reasons most often cited for not obtaining patient weight by the nursing staff were "patient too critically ill" and "other priorities of care exist." Both of these reasons exist primarily because the existing technology that is economically viable usually requires movement of the patient to a scale unit. "Almost by definition, if a patient were in an intensive care unit, he/she was too sick to be weighed by either the conventional standing or the litter scale method."
Problems in weight monitoring arise, as indicated above, including when a 100-pound nurse is confronted with moving a 200-pound bedridden patient to a scale. It is seen, therefore, that a need exists for simple, reliable, effective and relatively low cost equipment. This equipment should be able to be installed conveniently in an existing hospital bed for weighing a patient supported by the bed.